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Paper 2 Flashcards

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1
Q

What is the functional group of alcohols?

A

-OH

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2
Q

What is the general formula of alcohols?

A

CnH2n+1OH

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3
Q

What are the properties of alcohols?

A

Flammable - can undergo complete combustion

Soluble - solution will have a neutral PH

Oxidised to form Carboxylic acid with (potassium dichromate (VI) and heat)

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4
Q

What happens when we oxidise an alcohol?

A

A carboxylic acid is formed

Potassium Dichromate (VI) is required and heat

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5
Q

What is the colour change of oxidation of alcohol using potassium dichromate (VI)

A

Potassium Dichromate (VI) turns from orange to green

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6
Q

What are the 3 ways alcohol can be oxidised?

A

Using an oxidising agent (potassium dichromate VI) in dilute sulfuric acid

Microbial oxidation - Carboxylic acid is produced as a by product as they use alcohol as their energy source

Combustion

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7
Q

What are the uses of alcohols?

A

Used as fuel

As solvents in industry

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8
Q

State two ways to produce ethanol?
Conditions

A

Ethen + steam: - Addition reaction
Phosphoric acid catalysts
300 degrees
60-70 atm pressure

Fermentation of glucose by yeast: - Anaerobic respiration
Requires yeast
30-40 degrees
Anaerobic conditions

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9
Q

Chemical equation for production of ethanol through hydration?

A

C2H4 + H20 -> C2H5OH

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10
Q

Chemical equation for production of ethanol through fermnetation?

A

C6H12O6 -> C2H5OH + CO2

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11
Q

Advantages and disadvantages of production of ethanol through hydration?

A

Pros:
No waste products - efficient
Cheap process

Cons:
Ethene is made from crude oil which is a finite resource

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12
Q

Advantages and disadvantages of production of ethanol through fermentation?

A

Pros:
Glucose is a renewable resource
Yeast are easy to grow

Cons:
Process is relatively slow
Ethanol is weak and not pure so has to be distilled and purified

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13
Q

Functional group of Carboxylic acid?

A

-COOH

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14
Q

Are carboxylic acids strong or weak acids?

What does that mean?

A

Weak acids - they don’t fully ionise.

All the carboxylic acids don’t all release their hydrogen ions

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15
Q

What happens when carboxylic acids react with metal carbonates?

A

Salt (magnesium ethanoate) + Water + Carbon Dioxide

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16
Q

What happens when carboxylic acids react with metals?

A

Salt + Hydrogen

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17
Q

How are carboxylic acids made?

A

By oxidising an alcohol

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18
Q

What are carboxylic acids used for?

A

Ethanoic acid is dissolved in water to make vinegar:

This is used for flavourings and preserving foods

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19
Q

What is the functional group of an ester?

Where is it found?

A

-COO- functional group found in the middle of the molecule

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20
Q

Alcohol + Carboxylic acid (with an acid catalyst) ->

A

Ester + water

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21
Q

How do we name an ester?

A

Alcohol forms the first part and acid forms the second part

eg. Methyl Propanoate

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22
Q

Characteristics of esters?

A

Pleasant smells (Sweet or fruity)

Volatile (Evaporate easily)

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23
Q

How do we make an ester? Method

Use ethyl ethanoate?

A

Ethanoic acid + Ethanol

  1. Add a few drops of concentrated sulfuric acid to a boiling tube using a dropping pipette
  2. Add 10 drops of ethanoic acid
  3. Add an equal volume of ethanol
  4. Place boiling tube, in a beaker of water, on a tripod.
  5. Heat till the water boils and then allow to cool
  6. Once it’s cool pour the mixture into a test tube of sodium carbonate solution and mix
  7. Layer of ester should form on the top (sweet smell)
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24
Q

Why does water form when an alcohol and carboxylic acid react?

A

As the carboxylic acid loses the -OH from its -COOH functional group
And the alcohol lose the H from its -OH functional group

These combine to form H2O

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25
How are polyesters formed?
Using a diol and dicarboxylic acid
26
What does the dicarboxylic acid lose and diol lose to form a polyester?
Dicarboxylic acid loses - OH Diol loses - H
27
How do you name polyesters?
Ester in brackets and add poly to the outside. eg. Poly(Ethyl ethanoate)
28
How are some polyesters disposed of?
There are some polyesters that can biodegrade - these are called biopolyesters. Bacteria and microorganisms can break down the ester links They don't stay in landfill forever and this therefore reduces the pollutant effect.
29
What is a dimer?
Two monomers combined
30
What goes in the pipette and what goes in the burette during a titration?
Known concentration goes in the pipette and unknown in the burette
31
Steps of an acid - alkali titration when you're trying to find the concentration of acid?
1. Using a pipette add 25cm3 of alkali to a clean conical flask 2. Add a few drops of phenolphthalein to the conical flask and place it on a white tile (easier to see colour change) 3. Fill the burette with acid **below eye level** (don't want to be looking into the acid if it spills) and note the starting volume at eye level. 4. Slowly add the acid drop by drop, swirling the conical flask to mix. 5. Stop adding the acid when there is a colour change - **the acid has neutralised the alkali** 6. Note final acid in burette and calculate how much acid was added. 7. **Repeat titration until you get concordant results** - they are within 0.1 of each other. 8. Use the **concordant results** to calculate the mean volume of acid required to neutralise the alkali
32
Why do we swirl the conical flask when doing titration?
So the mixture is evenly distributed to ensure the colour change occurs as soon as the titration occurs as soon as the neutralisation takes place.
33
Colour of Litmus in acid and alkali
Acid - red Alkali - Blue
34
Colour of phenolphthalein in acid an alkali
Acid - colourless Alkaline - pink
35
Colour of methyl orange in acid an alkali
Acid - Red Alkaline - yellow
36
How are most metal oxides seperated?
Reduction using carbon (acts as a reducing agent) Cheapest and easiest method Copper oxide + carbon -> Copper + Carbon Dioxide
37
Why cant we reduce everything with carbon?
As some metals are more reactive than carbon Potassium Sodium Lithium Calcium Magnesium **Carbon**
38
What is above an below carbon in the reactivity series?
Magnesium Aluminium **Carbon** Zinc
39
What is metallic bonding?
The strong electrostatic force of attraction between the lattice of positive ions and the sea of delocalized electrons
40
Why is there a sea of delocalised electrons in metals?
As when the atoms are arranged in their lattice they give up their outer shell electrons and share them with each other
41
Why can ionic compounds only conduct electricity when molten or in solution?
As only then can the ions move through the structure and carry a charge
42
Why are metals good conductors of electricity and heat?
The delocalised electrons can carry thermal energy and electrical current throughout the structure
43
How are metals malleable?
Layers of ions in a metal can slide over each other
44
What does malleable mean?
Bent or hammered into shapes
45
What is an alloy made of?
2 or more different elements
46
Why are alloys harder than pure metal?
Different sized atoms distort the regular layers of metal atoms so they cannot slide over each other.
47
Which ions move where in electrolysis? What happens to them?
**Cations** (positive) move to the **cathode** (negative) and are **reduced** **Anions** (negative) move towards the **anode** (positive) and are **oxidised**
48
Why don't the electrodes react during electrolysis?
They're made of an inert material
49
What is an electrolyte?
An liquid or or solution that contains an ionic compound where ions are free to move
50
How do we set up an electrochemical cell for an aqueous solution?
Get two inter electrodes eg. graphite or platinum Clean the surfaces of the electrodes using emery paper Place both electrodes into a beaker with the electrolyte Connect the electrodes to a power supply using crocodile clips and wires.
51
Rules for electrolysis at the cathode in aqueous solution?
Cathode = Metals H+ ions and Metal Ions are attracted to the cathode **Hydrogen gas** will be produced if the metal is **more** reactive than hydrogen. If less reactive then that **pure metal will be produced**
52
Rules of electrolysis at the anode in aqueous solution?
Anode = non metals OH- and Non metal ions are present If an OH- ion and a **halide ion** is present then **that halide** will be produced If halides are not present **oxygen will be formed**
53
Half equation when oxygen is produced?
4OH- -> O2 +2H2O + 4e-
54
Method for how to make a soluble salt from an insoluble base and an acid?
Acid - Sulfuric Acid Base - Copper (II) Oxide 1. Heat acid in a water bath (in a fume cupboard) - speeds up reaction 2. Then add the base in excess to the acid - until base no longer dissolves 3. Filter off excess base - solution remaining is salt + water 4. Heat the solution gently to evaporate off some water 5. Stop heating when crystals begin to form on glass rod 6. Leave for 24 hours to crystallise. 7. Filter of solid crystals and leave to dry - left with copper sulfate crystals
55
How can we produce a dry sample of insoluble salt? Not method
Mix two soluble salts - Precipitation reaction eg. producing insoluble lead sulfate
56
Method for making dry lead (II) Sulfate?
Reactants: Lead Nitrate + Magnesium Sulfate 1. Add one spatula of lead to a test tube. Dissolve in **deionised water** to ensure there are no other ions. Shake. 2. Do the same with magnesium sulfate 3. Tip the two solutions into a beaker and stir 4. **Lead sulfate will precipitate out** 5. Filter off the lead sulfate using filter paper 6. Squirt deionised water into the beaker and filter again to ensure there is no lead sulfate left in the beaker 7. Rinse filter paper with deionised water to ensure no magnesium sulfate is present. 8. Scrape lead sulfate onto fresh filter paper and dry in oven or desiccator
57
How can we make a soluble salt using an acid/alkali reaction? Method
Using Titration: Measure out a set amount of acid into a conical flask using a pipette. Add a few drops of indicator Slowly add alkali drop by drop from the burette into the conical flask, whilst swirling. Do this until there is a colour change - acid neutralised Record volume of alkali added Now repeat without the indicator and add the recorded volume of alkali - no indicator so no contamination Remaining solution is salt + water Slowly evaporate off some of the water and then allow the solution to crystalise. Filter off the solid and dry it - pure dry salt
58
Volume of gas = ?
Moles of gas x 24 Volume must be dm^3
59
What is Avogadro's law?
One mole of any gas always occupies 24dm^3 at room temperature and pressure
60
Concentration in g/dm^3 = ?
mass / volume
61
Concentration is measure in?
Grams per dm^3 g/dm^3 Or Moles per dm^3 moles/dm^3
62
Concentration in mol/dm^3 = ?
Moles / volume
63
How do you convert from moles per dm3 to grams per dm3
Multiply by the Mr of the solution
64
Axis of reaction profile?
Y axis is energy X axis is progress of reaction
65
Describe a reaction profile for an exothermic reaction?
Products finish lower than reactants. So enthalpy change is negative - the vertical distance between the reactants and the products
66
What is the activation energy?
The minimum amount of energy the reactants need to collide with each other and react.
67
Describe the reaction profile of an endothermic reaction.
Products finish higher than reactants as they take in energy from the surroundings.
68
Endothermic or exothermic: Bond breaking?
Endothermic as energy must be supplied. Energy used to break the bonds is more than energy released forming them
69
Endothermic or exothermic: Bond forming?
Exothermic as energy is released when bonds are formed Energy released forming the bonds is greater than the energy required breaking them
70
Enthalpy change = ? (bond energies)
Total energy absorbed breaking the bonds - total energy released forming the bonds
71
formula for enthalpy change?
kj/mol
72
What is dynamic equilibrium?
When a reversible reaction occurs in a closed system then a state of equilibrium will be reached where the rate of the forward reaction is equal to the rate of the backwards reaction. The concentration of reactants and products will remain constant (given that there is no change to external conditions eg. Temperature or pressure)
73
Describe the thermal decomposition of ammonium chloride in terms of reversible reactions?
Ammonium Chloride is a white solid, when heated it breaks down into the gases ammonia and hydrogen chloride - forward reaction When cooled it reforms the white solid ammonium chloride as the ammonia and hydrogen chloride react
74
How does temperature affect a reversible reaction?
Adding heat: **Endothermic reaction** will increase to use up the extra heat. Removing heat: **Exothermic reaction** will speed up to give out more heat
75
How does pressure affect a reversible reaction?
Increasing pressure: Rate of reaction will increase on side which produces fewer moles of gas Decreasing pressure: Rate of reaction will increase on the side which produces more moles of gas
76
Why does a catalyst not affect the position of equilibrium?
Speeds up the reaction in both the forwards and backwards directions **by the same amount**
77
Define solubility
The maximum amount of a substance the will dissolve in a given amount of solvent at a fixed temperature
78
Unit of solubility
g per 100g of solvent
79
What happens to solubility as temperature increases?
Solubility increases
80
Investigating solubility method - practical?
Put 50 cm3 of water into a beaker Add salt to the water a little at a time until no more dissolves Filter to obtain the saturated solution and remove the excess Record the mass of an empty evaporating basin Pour the saturated solution into the evaporating basin Record the new mass Gently heat the evaporating basin and solution to remove **all the water** Record the mass of the evaporating basin an dry salt Calculate mass of water and dry salt
81
Formula for solubility?
Mass of solid / mass of water removed x 100
82
What is the functional group?
Group of atoms in a compound that determines its chemical properties and reactions

CHEMISTRY (19 decks)

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